Measurements of strains in wind turbine components provide valuable insight of the mechanical loads of components of wind turbines, for example turbine blades.
It is know to use strain gauge sensors and optical sensors in wind turbines. However, due to the very harsh operating conditions of wind turbines, the strain sensors should be very robust.
WO08020240 discloses a wind turbine blade incorporating an optical fibre configured for structural monitoring of the turbine blade. The optical fibre comprises at least one strain sensor. One end of the optical fibre is an output point, which is connected to a data processing device configured to process signals from the strain sensor. The other end of the optical fibre is an alternative output point, which is also connectable to the data processing device, such that in the event of a breakage in the optical fibre, signals from the strain sensor are available from at least one of the output points.
Whereas WO08020240 discloses a strain sensor having two output points so that the strain sensor is operable in the event of a breakage in the optical fibre, the strain sensor in WO08020240 is relatively complex. Hence, an improved strain sensor with a more robust design would be advantageous.